The present invention, in some embodiments thereof, relates to imaging and, more particularly, but not exclusively, to holographic imaging.
Techniques for capturing three-dimensional information from physical objects include tomography range-imaging and holography.
In tomography, several images of the object are captured from different points of view. Three-dimensional object information is then extracted by processing the successive images.
In range-imaging, the distance between the camera and various points on the surface of the object are measured, and a three-dimensional image or model of the object is constructed based on the measured distances. The distances are measured by illuminating the surface of the object with a laser and measuring the amount of time required for the laser light to travel between the object and the laser source. In some techniques a pattern is projected on the surface of the object using a scanning laser beam, and the deformation in the observed pattern is examined to determine the geometric information of the object.
In holography, holograms are constructed by recording the interference pattern of a coherent object bearing beam and a coherent reference beam. The image of the object is usually reconstructed by directing the same coherent reference beam at the holograms. Two standard techniques for the production of the holographs are known. In a first standard technique, the object is irradiated with laser light and an interference pattern between a reference wave and wave patterns reflected from the object are recorded in and a laser light-sensitive emulsion for the production of a hologram. In a second standard technique, an object wave is interrupted using a diffusing medium integral and the unobstructed or transmitted portion of the subject wave thus produced is caused to interfere with a reference wave.
International Patent Publication Nos. WO 2008/010790 and WO 2008/094141, the contents of which are hereby incorporated by reference, disclose a technique for capturing three-dimensional information of an object, using incoherent light such as reflected sunlight that is passively received from the object. The technique does not require interference between light scattered by the object and light not scattered by the object. An optical assembly transforms the received light and transmits the transformed light to an image capture assembly that captures a two-dimensional intensity image of the transformed light. The two-dimensional intensity image includes geometric information that is encoded as a Fresnel hologram. Information from a desired in-focus cross-section is extracted based on differences between patterns in that plane and in other planes.
Additional background art includes: Beck et al., “Synthetic-aperture imaging laser radar: laboratory demonstration and signal processing,” Appl. Opt. 44, 7621-7629 (2005); Mico et al., “Synthetic aperture superresolution with multiple off-axis holograms,” J. Opt. Soc. Am. A 23, 3162-3170 (2006); L. Martínez-León and B. Javidi, “Synthetic aperture single-exposure on-axis digital holography,” Opt. Express 16, 161-169 (2008); Indebetouw et al., “Scanning holographic microscopy with resolution exceeding the Rayleigh limit of the objective by superposition of off-axis holograms,” Appl. Opt. 46, 993-1000 (2007); J. Rosen, and G. Brooker “Digital spatially incoherent Fresnel holography,” Opt. Lett. 32, 912-914 (2007); J. Rosen, and G. Brooker, “Fluorescence incoherent color holography,” Opt. Express 15, 2244-2250 (2007); J. Rosen, and G. Brooker, “Non-Scanning Motionless Fluorescence Three-Dimensional Holographic Microscopy,” Nature Photonics 2, 190-195 (2008); and I. Yamaguchi and T. Zhang, “Phase-shifting digital holography,” Opt. Lett. 22, 1268-1270 (1997).